Hi Manok.

Here is a trick that I use to do it.

I open the Autopilot Panel (shift+8) and turn it on. While climbing, I press the Height (Alt Hold) button. Then I use "Ctrl+Z" followed by the the "+" (not the one on the numeric pad) to advance the altitude to the desired altitude. Leave the mouse pointer over the button so you can see it advance until you get to the altitude you require. This also sets the Vertical Speed to 1800 fpm.

I don't do this on the VC Autopilot because the ToolTip stops showing the changes after a few seconds, and I need to keep moving the mouse cursor around so they don't. I have another special reason for why I don't use the VC Autopilot for that too.  

Hope this helps.

Mark